Seekwatcher

Seekwatcher generates graphs from blktrace runs to help visualize IO
patterns and performance. It can plot multiple blktrace runs together,
making it easy to compare the differences between different benchmark runs.

Installation

Seekwatcher uses matplotlib
to generate graphs, and most distros have a package for this. You'll also need
to install python and the numpy module. It is common for the matplotlib
packages to depend on numpy, so installing a distro's matplotlib should get you
what you need.

Once those are setup, just copy the seekwatcher script to a bin directory
and make it executable.

For versions after 0.12, seekwatcher added some cython extensions to improve
performance. You will need to install the cython package from your distro, and
use python setup.py install to compile the extensions and install the resulting
files.

Running Seekwatcher

There are three basic ways to run seekwatcher. It can either generate
graphs from an existing blktrace run, start blktrace and run a program for
you, or make a series of pngs from a single trace. If seekwatcher starts and
stops blktrace, the trace runs are kept so they can be graphed again later.

Examples:

This will start blktrace on /dev/sda6, run find / > /dev/null, save the
blktrace output to find.trace and save the graph to find.png.

Finally, you can also make an animation (either ogg or mpg) of the IO
generated by a given run. For these images, a disk is simulated as a grid of
x,y coordinates and every sector read/written is plotted with a black square.
Squares fade as the IO ages, blanking out after 10 frames.

To create an animation from ext3.trace and store the resulting mpg
file in ext3-trace.mpg:

seekwatcher -t ext3.trace -o ext3-trace.mpg --movie

Seekwatcher creates 3 graphs by default: a plot of each sector read
or written, the number of seeks per second, and the throughput per second
during the run. Sometimes the plot of each sector can be difficult to read,
especially when comparing two runs with very different IO patterns.
seekwatcher --no-io-graph will disable this plot. Another option
is to use seekwatcher --zoom start:end to specify the range on the yaxis
you want included in the graph. The range is specified in MB, and using
a range of 0:0 will turn off seekwatcher's attempt at autoscaling the plot.

Seekwatcher uses a rolling average of the seek counts and throughput
values to make graphs smoother. You can control the number of seconds
rolled together (by default total trace time / 25) with
seekwatcher --rolling-avg

Controlling Output

By default, seekwatcher saves the graph into a file called trace.png.
seekwatcher -o filename can be used to save it to a different file. The
extension specified controls what type of file is created, choices include
.png, .jpg, .eps, and .svg. The resolution used can be controlled with
--dpi num. By default, seekwatcher uses a 8x6 pagesize and a dpi of 120.